An LD 50 dose S. typhi (strain Ty was injected intraperitoneally into white mice, and the number of micro-organisms was determined after 1 min. and subsequently, in the blood, and after 3 hr. and subsequently, in the spleen and liver. The course of the infection was observed for 34 days.

The number of bacteria gradually increased in the blood stream during the first post-infective hours. It was possible to differentiate by external signs from the sixth post-infective hour and onwards between sick animals and recovering ones. This difference corresponded to the bacterial concentration in the blood stream and internal organs.

In the sick animals the increase in the bacterial count of blood stream continued till 9–10 hr. after the inoculation, when it reached its first peak. During the following 8 hr. a clear decrease in the blood count was evident which was attributed to the ‘clearing mechanism’ of the blood. The onset of a new bacterial rise in the blood stream appeared 18 hr. after the inoculation and reached a second peak during the further 6–8 hr.

In contrast to the observed decrease in the bacterial blood count, a steady and gradual increase in the count of the internal organs was seen; it was steadily progressive till the exitus.

In the recovering animals a steady decrease in the bacterial blood count was recorded. Between 24 and 26 hr. the number of micro-organisms in the blood and spleen was found to be 400 times less in the recovering animals than in the moribund ones. From 48 hr. and onwards a slow and gradual decrease in the bacterial count of the surviving animals was observed. The blood became sterile after 25 days. In the spleen and liver of the surviving animals after 48 hr. a new increase in the bacterial count is evident, accompanied by hyperplasia of the spleen. The number of bacteria reached a new peak in the liver on the third day and in the spleen on the fourth day after the infection.

Subsequently a slow and gradual decrease in the bacterial count was observed in both organs, but even after 34 days a small number of persisting bacteria in the spleen and liver tissue may be found.

1. Fifteen apparently healthy persons were exposed to air enriched with positive or negative ions at 78° F. and 87° F. Average ion counts at 78° F. were 12,324 positive ions per ml. and 5,451 negative ions per ml. The averages at 87° F. were 14,865 positive ions per ml. and 5,442 negative ions per ml. Relative humidity was kept at 50% and air motion was 28 ft./min.

2. Seven sensations related to comfort (thermal sensation, humidity sensation, sensible perspiration, air motion, pleasantness, mood and fatigue) were recorded, pulse rate and oral temperature were measured.

3. In the experiments at 78° F. mood was improved (P < 0·001) by positive ionization. All other qualities remained unaffected by positive ionization. No effect was found under negative ionization at the ion concentration applied.

4. In the experiments at 87° F. five sensations (thermal sensation, sensible perspiration, pleasantness, mood and fatigue) were significantly (P < 0·001) improved by ionized air. In general, as can be seen from the significantly differences between grand means, the subjects felt cooler, perspired less, felt more pleasant, were in a better mood, and felt less fatigued under the influence of air enriched with ions.

Air motion sensation, humidity sensation, pulse rate and oral temperature were not affected by ionization.

5. As different individuals may vary in their response to ionization, individual preferences were tested. These tests indicated that at 87° F. six out of the fifteen persons tested preferred ionized air (P < 0·001). One person preferred air not enriched with ions (P = 0·0091).

In 1956–58 septic lesions in men of the R.A.F. accounted for about 3% of all admissions to sick-quarters or hospital and about 5% of admissions excluding respiratory disease; 1% of all men in the service were admitted with sepsis each year. Incidence fell with age, particularly up to the age of 25 years. The rates for women were about 50% higher.

Recruits experienced more than twice as much sepsis as trained men and boy apprentices. Officers had only half the admission rate of other ranks. These contrasts could have been explained by differences in age. There was no evidence of seasonal variation in the incidence of sepsis, but in recruits and boy apprentices epidemics of sepsis unrelated to season occurred.

I am indebted to Dr J. C. McDonald and Professor R. E. O. Williams for helpful criticism, to Professor P. Armitage for statistical advice and to the Director-General, Royal Air Force Medical Services, for permission to publish the results.

A longitudinal survey of respiratory illness in a Sheffield residential nursery is described. Over 8 months, outbreaks of respiratory illness occurred, two of which were associated with infection by Influenza A and Parainfluenza 3 viruses. The symptomatology is described of the illnesses resulting from these infections. The incidence of adenovirus recoveries over the same period was also investigated and suggests that adenoviruses of Types 1, 2 and 5 may be components of the normal viral flora of the nasopharynx in infants.

Coxsackie A 7 virus was isolated from thirty-seven patients during an outbreak in Scotland in 1959. Seven cases were paralytic, one of them fatal. Evidence is presented that Coxsackie A 7 virus caused these paralytic illnesses. The virus was also isolated from a paralytic case in 1956 and from a non-paralytic case in 1961. Serological surveys suggest that it has been active in the community for some years. Specific haemagglutination by Coxsackie A 7 virus was useful for rapid identification of viruses and for measurement of serum antibodies.

I am grateful to Dr A. D. Macrae of the Virus Reference Laboratory, Colindale, London, for prototype Coxsackie A 7 virus; to Dr K. Habel of the National Institutes of Health, Bethesda, U.S.A., for tissue culture-adapted ABIV virus; to Dr J. Wallace of the Blood Transfusion Service, West of Scotland Region, for samples of blood donor sera; to Dr M. Rentsch, Klinik für Kinderkrankheiten, University of Berne, Switzerland, for permission to quote the results of virological tests of his cases; to Miss R. McLelland, F.A.T.A., and to Mr C. McLean F.I.M.L.T., for technical assistance with animal experiments; to Mr H. G. Carson, F.I.M.L.T. and to Mr J. Kerr, A.I.M.L.T., for technical assistance with neutralization tests; and to the many clinical colleagues who provided specimens and information for this study.

This paper elaborates a concept of enrichment dynamics introduced in an earlier paper in which the author set out to find a labour saving technique for isolating salmonellac from sources other than faeces. Extensions to the concept are summarised in the Introduction. Explanations are given why a multiplicity of isolation procedures used in combination should normally yield more isolations than any one procedure alone.

Since a limit must always be set on the number of different media and procedures which can be used during routine examinations, a corresponding limit has also to be set on the combined efficiency of the procedures used. Not even a very laborious combination of methods can be expected to yield quite 100% of the isolations that are technically possible. When this rather unpalatable conclusion is accepted, a way is opened up for compromises between endeavour and reward, in terms of salmonella isolations. Judicious application of principles and methods discussed in these papers might be expected sometimes to lead to modifications in techniques which increase their efficiency, and in other cases to modifications which reduce labour without diminishing efficiency.

A description is given of a precipitin test, using potent non-infectious antigens, which can be performed in laboratories not specializing in virology. Trial of the method as a diagnostic procedure gave positive results in 100% of a series of 50 patients with acute poliomyelitis. Precipitation lines, almost always sharply defined and intense, were obtained in 89% of 33 sera within 3–8 days of onset of acute poliomyelitis and in all sera after the 8th day. In positive cases precipitation bands usually appeared within 24 hr. after starting the test. In all instances precipitation was homotypic with the type virus isolated from stools. Double bands appeared in very recent cases but only with homotypic precipitins. Single heterotypic lines appeared in 12 cases due to previous infection or perhaps due to infection by virus strains with common antigens. All control patients with nervous system disease other than poliomyelitis or with infection by Coxsackie or ECHO viruses and all control test animals gave negative results. Of 240 poorcommunity schoolchildren who had taken monovalent oral poliovaccine 4½ months previously, 80% had precipitins for Type 1, but less than 5% showed marked reactions. The sera from the remainder gave only weakly positive results. Contrasting with transience of precipitins, neutralizing antibodies persisted in nearly 100% of children tested.

The precipitin test was used to study antibody response to ingestion of trivalent oral vaccine (prepared and issued by the Poliomyelitis Research Foundation, Johannesburg). More than half (54 %) of 90 students who received the vaccine had positive precipitin-test results; most often these results appeared during the 2nd week after ingestion. In this positive group 54 % showed multiplication of at least two types and 12 % showed multiplication of all three types poliovirus.

Detailed instructions are given for the preparation of a purified and stabilized suspension of vaccinia elementary bodies. This is intended to take the place of crude glycerinated calf or sheep lymph vaccine. The technique consists of a series of procedures involving mechanical disintegration of the skin pulp, maintenance of dispersion by means of a non-ionic detergent, fractional centrifugation and bacterial disinfection. Stability of the purified virus is secured by suspending it in a dilute buffer containing peptone and polyvinylpyrrolidone. Experiments are described which illustrate the remarkable heat resistance of the virus in this suspending medium. The PVP-peptone also serves as an excellent menstruum for lyophilization. Production of this vaccine should be well within the competence of any properly equipped virus laboratory. Clinical trials are in progress.

All the work involved in the performance of the tissue culture assays was carried out by my former assistant Mr Edmund Bischoff. It is a pleasure to acknowledge both his technical skill and his enthusiasm. Mr T. C. Campbell provided the crude calf pulp used in the preparation of some of the purified suspensions.

Minimal quantities of active vaccinia virus in the form of a purified elementary body suspension were injected subcutaneously into rabbits. The amount administered was about 10 minimal infective doses as measured by intracutaneous titration and tissue culture assay: this is equivalent to about 1·3± 10−5μg of virus protein. The immune response to this minimal quantity of virus was determined by complement-fixation and virus neutralization tests and also by skin sensitivity tests. The results indicated that viral proliferation occurred to an extent sufficient to sensitize the tissues to the virus protein. Measurable amounts of antibody could also be detected in about one half of the experimental animals. A second inoculation of virus produced a considerable augmentation of the immune response. Viral proliferation must have taken place in order to evoke this immunity, but infection always remained at the subclinical level. The results were much improved when the infecting does of virus was incorporated in an adjuvant. DPT-polio vaccine functioned well as adjuvant but equally good results were obtained with a solution of polyvinylpyrrolidone. The latter substance also has valuable properties as a protective colloid and is thus able to maintain the viability of the virus over long periods of time.

On the evidence provided by these experiments it is suggested that an adequate immunity to smallpox might be achieved in man by similar methods. A primary sensitization could be achieved by incorporating a very small amount of active virus in one of the prophylactics given as a routine in the early months of life. This could be followed by normal jennerian vaccination a few months later; or the second inoculation of virus could also be incorporated in amultivalent prophylactic. For adults, a somewhat similar two-stage immunization would be required.

It is hoped that the publication of these preliminary experiments will encourage other investigators to continue what promises to be an important line of research.

All assays involving the use of monkey kidney tissue cultures were carried out by my former assistant Mr Edmund Bischoff. His help is gratefully acknowledged.

A controlled trial of Naseptin cream, as an anti-staphylococcaiprophylactic, made in two adult wards, showed the cream to be effective in reducing nasal carriage, including antibiotic resistant strains. There was no marked effect on wound infection.

A controlled trial of Naseptin cream and Sterzac powder prophylactically in maternity nurseries was found to be effective in reducing nasal carriage and infection.

These findings are discussed, and recommendations on the use of Naseptin cream as a prophylactic are made.

In toxoplasma-antibody titrations with the dye-test the tolerances of the parasite Toxoplasma gondii are approximately normally distributed on the logarithm of the serum dilution. Log LD 50 (the logarithm of the titre), the variance of the tolerance distribution and the variances of the sample distributions were estimated by probit analysis of data obtained with titrations of a serum which contained the antibody. An empirical expression was derived relating the fraction of parasites attacked by the antibody to the time of incubation with the antibody. Approximately the same values for the titre and the variance of the distribution were obtained for every incubation period between 20 min. and 4 hr.

The author is indebted to Mr J. C. A. Zaat and to Dr E. F. Drion of the Statistical Division of the Central Organization TNO for helpful discussions and assistance with the statistical calculations. The technical assistance of Miss A. K. Fast is gratefully acknowledged.

A preparation of vaccinia virus inactivated by ultra-violet irradiation under strictly controlled conditions, and shown to produce neutralizing antibody and resistance to challenge in rabbits, was active in only about half of 37 human volunteers. It was not, therefore, likely to be usefully immunogenic in man. In the largest single test, 15 of 25 men had unmodified primary skin reactions when challenged with living virus, although five of these had circulating antibody. On the other hand, only three of 10 men who responded to challenge with modified or negative reactions, had no circulating antibody.

In man the presence of circulating antibody does not necessarily indicate resistance to infection in the skin, nor does skin immunity always indicate the presence of circulating antibody.

1. Salmonella heidelberg infection in humans was traced to one cow excreting the organism in milk.

2. The cow was clinically normal and infection was confined to the right hind-quarter of the udder.

3. The affected quarter had numerous haemorrhagic foci but there was no inflammatory response to the infection.

4. Histological preparations suggested that Streptococcus uberis was causing a chronic mastitis in all four quarters.

Mechanical ventilation at 7 air changes/hr., air disinfection using vaporized hexyl resorcinol or α-hydroxy-α-methyl butyric acid, or irradiation of the air of the room above 8 ft. with ultraviolet radiation when applied to various clerical offices did not result in any observed alteration in the numbers of colds experienced by those working in them.

There were no differences in the numbers of colds experienced by those working in rooms of different sizes. The working population in these rooms varied from, about 20 to more than 80.

We should like to express our thanks to the Ministry of Pensions and National Insurance and to the Shell Petroleum Company, to those members of their staffs and to the nurses and others who helped us in this investigation. We should also like to thank the Shell Petroleum Company for the supply of α-hydroxy-α-methyl butyric acid, and the British Thomson Houston Company of Rugby for the loan of the ultraviolet lamp fittings.

1. The effect of blanket-disinfection on aerial contamination of exposed culture plates was studied during a six-month trial in six hospital units, containing a total of 270 beds.

2. Disinfecting blankets after use by each patient did not significantly reduce general bacterial or Staph. aureus counts on exposed culture plates.

3. Disinfected blankets were heavily recontaminated after only a few days' use. A quaternary-ammonium rinse during laundering conferred no self-disinfecting properties on them.

4. Cotton-cellular blankets were more economical and more popular with patients and nurses than were conventional woollen and two other types of cotton blanket.

Zone electrophoresis in a sugar concentration gradient is proposed as a complementary method for the biological classification of the enteroviruses. Under standardized experimental conditions it was found that the majority of the Coxsackie A viruses and the polioviruses have a common, low electrophoretic mobility. sackie A viruses and the polioviruses have a common, low electrophoretic mobility. The impression was gained that the ECHO viruses show the highest electrophoretic mobility, though in some cases there is overlapping with the Coxsackie Bs. The mobility of both of these groups is considerably higher than that of the other two.

Zone electrophoresis appears to be an excellent method for the purification of the enteroviruses prior to the production of specific precipitating antibodies.

Most air disinfectants fail at low relative humidity. Those which remain active appear to be the same compounds which, in other circumstances, can protect living cells against the lethal damage caused by freezing to low temperatures and then thawing. The compounds are either simple glycols, whose respective activities in the two fields are already known, or the weaker Lewis bases, whose air disinfectant properties have not hitherto been investigated. It is suggested that both freezing protection and bactericidal action are due to the special solvent properties of these compounds, which come into play when most of the water usually present has been removed, by freezing or by drying respectively.

I am indebted to Dr 0. M. Lidwell for the loan of air sampling equipment, and to Dr L. N. Owen and to the Shell Chemical Co. for the gift of various diols.

1. In two R.A.F. recruit stations between November 1958 and March 1959, there were 2603 admissions to Sick Quarters with respiratory illness. Throat swabs from 1129, and paired sera from 1197 were tested for certain respiratory viruses.

2. From the serological results it was estimated that 19% of the admissions were associated with influenza A infection, 7% with influenza B, 26% with adenovirus, 1% with para-influenza Type 1, 1% with para-influenza Type 3 and 8% with Coe virus, but as 21% of the identified infections were multiple the proportion of illness associated with one or more of these infections was only 50%. Thirty-four per cent of the Coe virus infections and 56% of the para-influenza virus infections were multiple.

3. Virus isolation test results led to a similar estimate of the frequency of adenovirus infection (23%) but to a lower estimate for Coe virus (3%) and for the para-influenza viruses, no systematic attempt was made to isolate influenza viruses. Reasons are given for thinking that most of the admissions associated with Coe virus infection in 1958, but few of those in 1959, were caused by this agent. The proportion of illnesses attributable to viruses of the para-influenza group was probably about 1%.

4. The main symptoms associated with Coe virus infection were upper respiratory. Hoarseness was rather more prominent than in other infections but the height and duration of fever and the frequency of febrile symptoms were less. The few illnesses associated with para-influenza virus infection had no obvious distinguishing features.

1960 survey

1. Blood specimens were taken from 205 recruits on their arrival at a recruit camp in January 1960 and immediately before their departure in March; 764 men in ten operational stations were bled in January and a sample of 260 were bled again in March.

2. The respiratory illness admission rate was 25% in the recruits and 4% in the trained men; 49% of the recruits showed a rise in antibody to one or more respiratory virus antigens compared with 2% in the other group. The high rate of infection in recruits was mainly due to adenovirus (36%) and Coe virus (20%).

3. It was estimated that about a third of the adenovirus infections and an eighth of the Coe virus infections were responsible for illness requiring admission. There was no indication that either infection caused any appreciable number of less severe illnesses not requiring admission.

4. Evidence from this survey and the earlier one suggests that the presence of neutralizing antibody to Coe virus does not prevent infection, though it appears to lower the probability of illness.

Over a certain range there is a linear relationship between the amount of complement required for 50 % lysis and the amounts of one of the variables in the primary reaction mixture of a complement-fixation test when the third variable is present in a quantity sufficient to allow maximum fixation.

If this linear relationship were maintained as the concentration of the selected variable is progressively reduced, there would also be a linear relationship between the logarithms of the amounts of complement fixed and the logarithms of the amounts of the selected variable; in this case, the line with logarithmic co-ordinates will necessarily have unit slope.

When the fixation of small amounts of complement by several virus systems is measured, an approximately linear relationship using logarithmic co-ordinates has been demonstrated, but in many cases the line does not have unit slope. In this range, therefore, there is not a linear relationship when arithmetic co-ordinates are used.

A new design for a complement-fixation test is proposed, using isohaemolytic curves.

The usefulness of the meningococcal CF test was assessed by investigating sera from (a) patients with meningococcal meningitis from whom meningococci had been isolated, and (b) patients with aseptic meningitis in whom no virus aetiology had been demonstrated and from whose C.S.F. no bacteria had been isolated.

Meningococcal CF antibodies were relatively strain-specific; cross-reacting anti-bodies to heterologous strains were irregular both qualitatively and quantitatively.

Positive meningococcal CF tests were obtained in 8 cases of aseptic meningitis, 3 showing a predominance of lymphocytes and 5 a predominance of polymorpho-nuclears in C.S.F. As a result of these positive tests, the cases of lymphocytic aseptic meningitis were given energetic antibiotic therapy to avoid the possibility of more chronic infection.

We wish to thank many clinical and bacteriological colleagues for their co-operation, and Prof. S. Graham for details of one case. We are grateful to Dr Patricia Bradstreet, Standards Laboratory for Serological Reagents, London, N.W. 9, for meningococcal agglutination results, and to Miss C. Gourlay for valuable technical assistance.